1. Field of the Invention
The invention pertains to the field of cushion rings. More particularly, the invention pertains to elastomer cushion rings that are bonded to at least one side of a sprocket.
2. Description of Related Art
Randomized sprockets for roller chains are known. U.S. Pat. No. 6,155,943, which is hereby incorporated herein by reference, discloses a roller chain and sprocket drive with a randomized sprocket which modulates the roller position on the sprocket by varying the radial seating position of the roller while maintaining a constant chordal dimension between seated rollers. The roots between teeth of the sprocket have radii that vary between a nominal radius, a maximum radius, and a minimum radius. This variation or randomization is intended to provide a noise modulation effect while avoiding the negative effects of high impact from conventional randomized sprockets.
Roller chain sprockets oriented to minimize strand length variation of the chain are also known. U.S. Pat. No. 6,213,905, which is hereby incorporated herein by reference, discloses a roller chain and sprocket drive which has at least two sprockets with varied radial seating positions. The relative orientations of the sprockets are adjusted to provide favorable dynamics to the drive. This includes minimizing strand variation and providing the maximum strand variation for each chain strand to be phased differently than other strands.
Elastomer cushion rings are also known for conventional sprockets with equally spaced teeth. U.S. Patent Application Publication No. 2003/0176251 discloses a method of installing a cushion ring on a sprocket body that includes applying a force to the cushion ring so that an opening in the cushion ring is deformed to a shape that accommodates passage of a non-circular flange of the sprocket body through the cushion ring. After the non-circular flange of the sprocket body is inserted through the opening of the cushion ring, the deforming force is released from the cushion ring so that the cushion ring is trapped between the flange and another portion of the sprocket body. The sprocket assembly includes at least one and typically two cushion rings trapped by respective non-circular flanges.
U.S. Patent Application Publication No. 2002/0169044 discloses a sprocket with a hub and a plurality of teeth projecting radially outwardly from the hub. At least one cushion ring is located adjacent to the teeth, and the cushion ring defines a plurality of compression pads separated from each other by transverse grooves. Each of the compression pads is defined symmetrically about a circumferential mid-point. The cushion ring, when part of a sprocket with symmetric tooth spacings, is operable identically in first and second opposite rotational directions. In one arrangement, the compression pads each include a planar outer surface having a leading and a trailing end, where the leading end and trailing end are located a common radial distance from the center of the hub about which the sprocket rotates. The tooth spaces of the sprocket may be symmetric or asymmetric, and the root surface may be relieved. The sprocket may include multiple tooth profiles distributed randomly about the hub.
U.S. Pat. Nos. 6,179,741 and 6,371,875 disclose a roller chain sprocket with sprocket teeth each having an engaging flank and a disengaging flank. The engaging flank of a first tooth of the sprocket cooperates with the disengaging flank of a second tooth to define a tooth space having a root surface extending between the engaging flank and the disengaging flank. The root surface has a first root surface portion defined by a first radius extending from an arc center of the first root surface portion. A cushion ring is mounted to a first face of the sprocket and has a number of alternating compression pads and grooves. A first groove has a first groove portion defined by a second radius extending from an arc center of the first groove portion. The arc center of the first groove portion is positioned at least proximate to a radial line extending between a center of the sprocket and the arc center of the first root surface portion. A first compression pad has an inclined outer surface defined by a leading edge that is spaced radially inward relative to a trailing edge. The leading edge is also positioned radially inward from the engaging flank of the first tooth, and the trailing edge is positioned radially inward from a disengaging flank of the first tooth.
As can be seen, the above listed prior art sprocket tooth angular spacing is repetitive and is equal to 360 degrees divided by the number of sprocket teeth. Repetitive sprocket tooth spacing is known to create undesirable chain engagement noise having orders that are related to the number of sprocket teeth. A random tooth sprocket has both irregular angular spacing and varying pitch radii of the sprocket teeth which disrupts the repetitive chain engagement noise orders.